Spreader element for manufacturing unidirectional fiber-reinforced tapes

ABSTRACT

Disclosed is a fiber-reinforced composite and methods and apparatuses for making the same. Some fiber-reinforced composites include a matrix material including a thermoplastic material and a non-woven fibrous region having a plurality of continuous fibers dispersed in the matrix material, wherein the width and the length of the non-woven fibrous region are substantially equal to the width and the length, respectively, of the liber-reinforced composite, wherein the non-woven fibrous region has a mean relative area fiber coverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV) (%) of from 3 to 20, and wherein each of the plurality of continuous fibers is substantially aligned with the length of the fiber-reinforced composite.

CROSS REFERENCE TO RELATED APPLICATIONS

“This is a continuation of U.S. nonprovisional patent application Ser.No. 15/556,845, filed Sep. 8, 2017, which is a national stageapplication filed under 35 U.S.C. § 371 of international applicationPCT/IB2016/000392, filed Mar. 10, 2016, which claims priority to U.S.Provisional Patent Application No. 62/131,002, filed Mar. 10, 2015, theentirety of which applications are hereby incorporated by referenceherein.”

BACKGROUND OF THE INVENTION A. Field of the Invention

The present invention generally concerns unidirectional (UD)fiber-reinforced composites and apparatus and methods for making thesame. In particular, some UD fiber-reinforced composites have anon-woven fibrous region or layer comprising a plurality of continuousfibers dispersed in a polymeric matrix, where the non-woven fibrousregion has a substantially uniform density as defined by a mean relativefiber area coverage (RFAC) (%) and an associated coefficient of variance(COV) (%). The polymeric matrix can be a thermoplastic or thermosetpolymeric matrix.

B. Description of Related Art

Composite materials can include fibers dispersed in resin/polymericmatrix. Such composite materials are useful in various industries, suchas, for example, in the consumer electronics, ballistics, aerospace, andtransportation industries. A UD composite is a composite having fibersthat extend in substantially one direction. UD composites, havinganisotropic properties, can be used to make articles of manufacturehaving properties that vary in one or more directions or dimensions.

An example of UD composite is a LD tape or prepreg, which may becharacterized as a thin strip or band of continuous UD fibers (e.g,glass fibers, carbon fibers, and/or the like) impregnated with a polymerresin. Such UD tapes can have a width of from 1 to 15 cm, perhaps wider,and a thickness of less than 1 mm. Such UD tapes may be provided on aspool or reel. UD tapes are described in U.S. Pat. No. 6,919,118 toBompard et al. and U. S. Publication No. 2014/0147620 to Li et al.

In theory, all fibers in a UD composite should be uniform, parallel, andcontinuous; however, in practice, such properties are difficult toachieve. For example, commonly available UD tapes may have fibrousregions or layers that include non-uniform arrangements of fibers, airpockets or voids, broken fibers, and/or the like. There have beennumerous attempts to address these problems.

U.S. Pat. No. 5,496,602 to Wai attempts to solve these problems viaforming a UD tape by placing UD fibers between a pair of epoxy thermosetresin films and heating the fibers and films. The UD tape is laterinjected with a polymer to fill interstices between the fibers. Due tofiber movement during application of the films, the resulting UD tapemay include a non-uniform arrangement of fibers as well as air pocketsor voids. Further, Wai's method includes a number of relatively complexsteps as well as the introduction of materials, such as epoxy, that maynot be desirable.

Some attempts to solve these problems include the use of fiber spreadingdevices. U.S. Pat. No. 5,101,542 to Narihito describes such a fiberspreading device, which includes a plurality of roller elements, eachhaving a continuously convex outer surface that bulges at its center.U.S. Pat. No. 8,191,215 to Meyer describes a rotating fiber spreadingdevice that includes wings, each having an outer-most spreading edgethat is continuously convex in cross-section. U.S. Pat. No. 8,470,114and U.S. Publication No. 2013/0164501 to Jung et al. each describemethods of spreading fibers by passing the fibers over a series ofconvex bars. U.S. Pat. No. 6,585,842 to Bompard et al. describes amethod of spreading fibers by passing the fibers over a series of curved(e.g., banana-shaped) rollers.

Some attempts to solve the above-identified problems include the use ofimpregnation devices. Typical impregnation processes include the use ofbaths of polymeric solutions through which a fiber layer may be moved.In such a process, the polymeric solution may be pressed into the fiberlayer using a roller. Wai's process, described above, impregnates afiber layer by pressing polymer films on opposing sides of the layerinto the layer. Each of these processes are similar in that they involvepressing a polymeric resin material into a fiber layer to achieveimpregnation of the fiber layer.

While such fiber spreading and impregnation devices and processes may beused to prepare a UD tape, such a UD tape still suffers from non-uniformfiber arrangement and air pockets or voids in the matrix material. Forexample, FIG. 1 includes cross-sectional images of commerciallyavailable UD composites, obtained using a scanning electron microscope.These commercially available UD composites possess fibrous regionshaving non-uniform fiber arrangements, and thus non-uniform densities,as well as voids and air pockets in the polymeric matrix.

SUMMARY OF THE INVENTION

Discoveries have been made that solve, or, at least alleviate, theproblems of non-uniform distribution of fibers, voids and air pockets,and/or the like in UD composite tapes. In particular, fiber-reinforcedcomposites of the present disclosure can have a non-woven fibrous regionor layer comprising a plurality of continuous fibers dispersed in apolymeric matrix. The polymeric matrix can be a thermoset, or morepreferably, a thermoplastic polymeric matrix. Thermoplastic polymericmatrices may be moldable and pliable above a certain temperature and maysolidify below the temperature. Once cured or cross-linked, thermosetpolymeric matrices tend to lose the ability to become moldable orpliable with increased temperature. Polymeric matrices can be includedin a composition having thermoplastic or non-thermoplastic polymer(s),additives, and/or the like. The non-woven fibrous region can have asubstantially uniform density as defined by a mean relative fiber areacoverage (RFAC) (%) of from 65 to 90 and a coefficient of variance (COV)(%) of from 3 to 20, preferably a mean RFAC (%) of from 69 to 90 and aCOV (%) of from 3 to 15, or more preferably a mean RFAC (%) of from 75to 90 and a COV (%) of from 3 to 8. A fiber-reinforced composite of thepresent disclosure, at least by virtue of having such a substantiallyuniform density, may include a volume fraction of voids that is lessthan 5%, preferably less than 3%, or more preferably less than 1%.Fiber-reinforced composites of the present disclosure can be used in avariety of articles of manufacture.

Also disclosed are systems and methods for spreading fiber bundle(s) ortow(s) into spreaded fiber layer(s) and/or impregnating spreaded fiberlayer(s) with a matrix material to produce fiber-reinforced compositesof the present disclosure. Some systems include both a spreading unitand an impregnation unit, with the impregnation unit positioneddownstream from the spreading unit. Such a spreading unit can utilize aspreading element having two different surfaces (e.g., a convex surfaceand a concave or planar surface) that meet at a (e.g., rounded) edge tospread fibers from fiber bundle(s) in an efficient and uniform mannerinto spreaded or flattened fiber layer(s). Such an impregnation unit maybe configured to receive at least two spreaded or flattened fiberlayers, position a thermoplastic or thermoset polymeric resin betweenthe two fiber layers, and press the two fiber layers into the resin,thereby forming a non-woven fibrous region of a composite of the presentdisclosure. Each of the two spreaded or flattened fiber layers caninclude fibers from one or more fiber bundles, such as, for example, 1,2, 3, 4, 5, 6, 7, 8, 9, 10, or more fiber bundles.

In one aspect, there is disclosed a fiber-reinforced composite thatincludes a polymeric matrix and a non-woven fibrous region comprising aplurality of continuous fibers dispersed in the polymeric matrix, thenon-woven fibrous region having a substantially uniform density asdefined by a mean RFAC (%) of from 65 to 90 and a COV (%) of from 3 to20. In more preferred embodiments, the non-woven fibrous region has amean RFAC (%) of from 69 to 90 and a COV (%) of from 3 to 15. In stillfurther preferred embodiments, the non-woven fibrous region has a meanRFAC (%) of from 75 to 90 and a COV (%) of from 3 to 8. The width andthe length of the non-woven fibrous region can be substantially similarto the width and the length, respectively, of the fiber-reinforcedcomposite, the plurality of continuous fibers can be unidirectionallyoriented and substantially parallel to a first axis, and thefiber-reinforced composite can include, by volume, at least 35 to 70%,preferably 40 to 65%, or more preferably 45 to 55%, of the plurality ofcontinuous fibers. A fiber-reinforced composite can have a width of upto 6 meters and a length of up to 10,000 meters.

In some fiber-reinforced composites, a first fiber layer and a secondfiber layer are pressed or squeezed together to form the non-wovenfibrous region. The non-woven fibrous region can include fibers from aplurality of fiber bundles, each bundle including from 1,000 to 60,000individual filaments. The average cross-sectional area of the individualfilaments can be from 7 μm² to 800 μm². Non-limiting examples ofcontinuous fibers include glass fibers, carbon fibers, aramid fibers,polyethylene fibers, polyester fibers, polyamide fibers, basalt fibers,steel fibers, or a combination thereof. Such glass fibers can have anaverage filament cross-sectional area of from 75 μm² to 460 μm² and suchcarbon fibers can have an average filament cross-sectional area of from7 μm⁷ to 60 μm².

In some fiber-reinforced composites, the polymeric matrix can be athermoplastic matrix or a thermoset matrix, with thermoplastic matricesbeing preferred. The polymeric matrix of a fiber-reinforced compositecan be structured such that the fiber-reinforced composite has a firstpolymeric-rich region and a second polymeric-rich region, where thenon-woven fibrous region is positioned between the first and secondpolymeric-rich regions. Polymeric-rich regions include those having lessthan 10%, less than 5%, or less than 1^(%), by volume, of continuousfibers. The width and the length of polymeric-rich region(s) can besubstantially similar to the width and the length, respectively, of therespective fiber-reinforced composite. In one embodiment, the thicknessof the first polymeric-rich region and the thickness of the secondpolymeric-rich region are the same or are within 10%, preferably 5%, andmore preferably 1%, of one another. In one embodiment, the thicknessesof the first and second polymeric-rich regions vary by more than 10, 15,or 20% with respect to one another. Each of the first and secondpolymeric-regions can have a substantially uniform density (e.g., massper unit volume) throughout the polymeric-rich region.

The polymeric matrix of fiber-reinforced composites of the presentdisclosure can include thermoplastic polymers, thermoset polymers,co-polymers thereof, or blends thereof. Non-limiting examples ofthermoplastic polymers include polyethylene terephthalate (PET),polycarbonates (PC), polybutylene terephthalate (PBT),poly(1,4-cyclohexylidene cyclohexane-1,4-dicarboxylate) (PCCD), glycolmodified polycyclohexyl terephthalate (PCTG), poly(phenylene oxide)(PPO), polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC),polystyrene (PS), polymethyl methacrylate (PMMA), polyethyleneimine orpolyetherimide (PEI) or derivatives thereof, thermoplastic elastomers(TPE), terephthalic acid (TPA) elastomers, poly(cyclohexanedimethyleneterephthalate) (PCT), polyethylene naphthalate (PEN), polyamides (PA),polysulfone sulfonate (PSS), polyether ether ketone (PEEK), polyetherketone ketone (PEKK), acrylonitrile butyldiene styrene (ABS),polyphenylene sulfide (PPS), co-polymers thereof, or blends thereof.More preferred thermoplastic polymers include polypropylene, polyamides,polyethylene terephthalate, polycarbonates (PC), polybutyleneterephthalate, poly(phenylene oxide) (PPO), polyetherimide,polyethylene, co-polymers thereof, or blends thereof. Even morepreferred thermoplastic polymers include polypropylene, polyethylene,polyamides, polycarbonates (PC), co-polymers thereof, or blends thereof.

Non-limiting examples of thermoset polymers suitable for use as a matrixmaterial in the present fiber-reinforced composites include unsaturatedpolyester resins, polyurethanes, bakelite, duroplast, urea-formaldehyde,diallyl-phthalate, epoxy resin, epoxy vinylesters, polyimides, cyanateesters of polycyanurates, dicyclopentadiene, phenolics, benzoxazines,co-polymers thereof, or blends thereof. A polymeric matrix of one of thepresent fiber-reinforced composites can be included in a compositionalong with one or more additives. Non-limiting examples of suchadditives include coupling agents to promote adhesion between thepolymeric matrix and continuous fibers, antioxidants, heat stabilizers,flow modifiers, flame retardants, UV stabilizers, UV absorbers, impactmodifiers, cross-linking agents, colorants, or a combination thereof.

Some of the present fiber-reinforced composites do not includepolypropylene and do not include glass fibers. Some of the presentfiber-reinforced composites do not include polyethylene and do notinclude glass fibers. Some of the present fiber-reinforced compositesinclude polypropylene and/or polyethylene, but do not include glassfibers. Some of the present fiber-reinforced composites include glassfibers, but do not include polypropylene or polyethylene.

Also disclosed are laminates including fiber-reinforced composites ofthe present disclosure. Such laminates can include 2, 3, 4, 5, 6, 7, 8,9, 10, or more plies, where one ply may consist of one fiber-reinforcedcomposite of the present disclosure. In some laminates, at least twoplies are positioned such that their respective fibers are substantiallyparallel to a first axis. In some laminates, at least two plies arepositioned such that their respective fibers are not parallel to eachother. Fiber-reinforced composites and laminates of the presentdisclosure can be assembled or processed into two-dimensional orthree-dimensional structures, such as, for example, via winding and/orlay-up techniques.

Also disclosed is an article of manufacture that includes any of thefiber-reinforced composites or laminates of the present disclosure.Non-limiting examples of such articles of manufacture include automotiveparts (e.g., doors, hoods, bumpers, A-beams, B-beams, battery casings,bodies in white, reinforcements, cross beams, seat structures,suspension components, hoses, and/or the like), braided structures,woven structures, filament wound structures (e.g., pipes, pressurevessels, and/or the like), aircraft parts (e.g., wings, bodies, tails,stabilizers, and/or the like), wind turbine blades, boat hulls, boatdecks, rail cars, sporting goods, window lineals, pilings, docks,reinforced wood beams, retrofitted concrete structures, reinforcedextrusion or injection moldings, hard disk drive (HDD) or solid statedrive (SSD) casings, TV frames, smartphone mid-frames, smartphoneunibody casings, tablet mid-frames, tablet unibody casings, TV stands ortables, lap-top computer casings, ropes, cables, protective apparel(e.g., cut-resistant gloves, helmets, and/or the like), armor, plates,and/or the like.

The present disclosure includes spreading units configured to spread oneor more fiber bundles, each having a plurality of fibers, into one ormore spreaded fiber layers. A fiber bundle can be spread in a directionthat is perpendicular to a long dimension of the fiber bundle, therebyforming a spreaded or flattened fiber layer. A spreading unit caninclude a spreading element having at least one lobe comprising a firstsurface with a convex first profile and a second surface with a secondprofile that is different than the first profile, wherein the first andsecond surfaces meet to form a (e.g., rounded) edge, and wherein thelobe is configured to spread a plurality of fibers from a fiber bundlein a lateral direction when the plurality of fibers contact the firstsurface and the edge. Such a second profile can be substantiallystraight or concave. A spreading element can be positioned such that aplurality of fibers contacts the second surface and transitions to thefirst surface (e.g., across the edge). A spreading element can bepositioned such that a plurality of fibers contacts the first surfaceand transitions to the second surface (e.g., across the edge). For aspreading element including two or more lobes, second surfaces of thetwo or more lobes can be contiguous, such that, for example, if thesecond surfaces are planar, the second surfaces cooperate to form acontinuous flat surface.

In some spreading units, a spreading element can be rotated relative toa plurality of fibers being spread by the spreading element and about alongitudinal axis of the spreading element, such rotation can be in anoscillating fashion. A spreading element can be configured to oscillaterelative to a plurality of fibers being spread by the spreading elementand in a direction that is substantially perpendicular to the longdimension of the plurality of fibers. Such oscillation can be at anamplitude of from 0.1 to 20 mm, preferably 0.1 to 10 mm, and at afrequency of from 0.1 to 5 Hz, preferably 0.5 to 2 Hz.

In some spreading units, one or more holding elements can be positionedupstream and/or downstream of a spreading element, wherein each holdingelement is configured to reduce lateral movement of a plurality offibers as the plurality of fibers are spread by the spreading element.Such holding element(s) can each include one or more grooves configuredto receive the plurality of fibers.

A spreading unit of the present disclosure can include at least firstand second spreading elements, the second spreading element beingpositioned downstream of the first spreading element. Lobe(s) of thesecond spreading element can be larger than lobe(s) of the firstspreading element (e.g., by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more %)(e.g., in a length, width, height, radius, transverse dimension, and/orthe like). The first and second spreading elements may cooperate tospread one or more fiber bundle(s) into one or more fiber layer(s). Thefirst spreading element can include at least first and second lobes andthe second spreading element can include at least third and fourthlobes, where the first and third lobes are configured to spread a firstfiber bundle and the second and fourth lobes are configured to spread asecond fiber bundle. Such a spreading unit can

The spreading unit can include a third spreading element having at leastfifth and sixth lobes and a fourth spreading element having at least aseventh and an eighth lobes, where the fifth and seventh lobes areconfigured to spread a third fiber bundle and the sixth and eighth lobesare configured so spread a fourth fiber bundle. The spreading unit canbe configured to form a first flattened fiber layer from the first andsecond fiber bundles and a second flattened fiber layer from the thirdand fourth fiber bundles.

One or more tensioners can be positioned upstream of a spreading unit,each configured to tension one or more fiber bundle(s) during spreadingof the fiber bundle(s). A heat source can be provided at, upstream of,and/or downstream of a spreading unit, the heat source configured toheat a plurality of fibers being spread by the spreading unit. A heatsource may include an infrared heat source, a heated spreading element,a heated holding element, and/or the like. A fiber bundle feed unit canbe positioned upstream of the spreading unit, the fiber bundle feed unitbeing configured to provide one or more fiber bundles to the spreadingunit.

Also disclosed is a method for producing at least one flattened fiberlayer from one or more fiber bundles, each having a plurality of fibers.Such a fiber bundle can include 1,000, 2,000, 3,000, 4,000, 5,000,10,000, 20,000, 30,000, 40,000, 50,000 60,000, or more individualfilaments. Such a flattened fiber layer can be produced at a rate offrom 1 to 50 in/min, preferably 2 to 25 m/min, and more preferably from8 to 15 m/minute.

Also disclosed is an impregnation unit for dispersing a plurality offibers within a thermoplastic or thermoset polymer matrix material. Theimpregnation unit can include a first flattened fiber layer feedcomprising a first flattened fiber layer, a second flattened fiber layerfeed comprising a second flattened fiber layer, a thermoplastic orthermoset polymer matrix material feed comprising a thermoplastic orthermoset polymer matrix material and configured to dispose the matrixmaterial between the first and second flattened fiber layers, and apressing device configured to press the first and/or second flattenedfiber layers into the matrix material. Such an impregnation unit caninclude one, two, three, or more rubbing elements configured to contactat least one of the first and second spreaded fiber layers after thespreaded fiber layer has been pressed into the matrix material and tooscillate in a direction that is substantially perpendicular to a longdimension of the spreaded fiber layer. Such rubbing elements mayoscillate at an amplitude of from 0.1 to 20 mm, preferably 0.1 to 10 mm,and at a frequency of from 0.1 to 5 Hz, preferably 0.5 to 2 Hz. Eachrubbing element can include a plurality of rounded segments, lobes, orconvexities positioned laterally along its longitudinal axis.

A polymer matrix material feed can include an extruder configured toextrude the matrix material (e.g., as a sheet or a film; for example,out of a slit die) between the first and second flattened fiber layers.Such an extruder may reduce drip-related wastage. The extruder may beconfigured to provide material directly onto the first and/or secondflattened fiber layers.

Also disclosed are methods for dispersing a plurality of fibers into athermoplastic or thermoset polymeric matrix material. Some methodsinclude obtaining a stack of a first flattened fiber layer, a secondflattened fiber layer, and thermoplastic or thermoset polymeric matrixmaterial disposed between the first and second flattened fibers, andpressing the first and/or second flattened fiber layers into the matrixmaterial. Such pressing may be performed using stationary or rotatingrollers, pins, rods, plates, and/or the like.

The present systems and methods may be used to produce afiber-reinforced composite of the present disclosure at a rate of from 1to 50 m/min, preferably 2 to 25 m/min, and more preferably 8 to 15m/min.

Also disclosed is a composition including a first flattened fiber layercomprising a plurality of fibers from a first fiber bundle, a secondflattened fiber layer comprising a plurality of fibers from a secondfiber bundle, and a thermoplastic or thermoset polymer matrix materialpositioned between the first and second flattened fiber layers, whereinthe first and/or second flattened fiber layers have been formed usingspreading element(s) of the present disclosure. The thermoplastic orthermoset polymeric matrix material can comprise a sheet or a film intowhich the first and second spreaded fiber layers can be pressed to forma fiber-reinforced composite.

The term “coupled” is defined as connected, although not necessarilydirectly, and not necessarily mechanically; two items that are “coupled”may be unitary with each other. The terms “a” and “an” are defined asone or more unless this disclosure explicitly requires otherwise. Theterm “substantially” is defined as largely, but not necessarily wholly,what is specified (and includes what is specified, e.g., substantially90 degrees includes 90 degrees and substantially parallel includesparallel), as understood by a person of ordinary skill in the art. Inany disclosed embodiment, the terms “substantially,” “approximately,”and “about” may be substituted with “within [a percentage] of” what isspecified, where the percentage includes 0.1, 1, 5, and 10 percent.

The terms “flattened” and “spreaded” are synonymous in the presentapplication. As used in this disclosure, “flattened,” “flattening,”“spreaded,” and “spreading” may each be used in connection with aprocess through which a fiber bundle is widened in a lateral direction,or a direction that is substantially perpendicular to a long dimensionof the fiber bundle, such that, for example, the fiber bundle becomesthinner when viewed from the side. Typically, a fiber bundle can beflattened or spreaded such that a resulting flattened or spreaded fiberlayer has, on average, a thickness or depth of 1 to 8 filaments,preferably 3 to 6 filaments, and more preferably 4 to 5 filaments.Nevertheless, other thicknesses or depths are also contemplated.

The term “non-woven” is used to describe a structure made of continuousfibers that does not have a woven architecture. In fiber-reinforcedcomposites of the present disclosure, a non-woven fibrous region mayinclude filaments that cross over other filaments. Such cross-over,which may affect the density of the fibrous region, does not change thenon-woven nature of the fibrous region.

The term “ply” refers to a single layer, and “plies” is the plural formof ply.

The term “void” refers to a gas pocket within a fiber-reinforcedcomposite. The void volume fraction of a composite may be determined bytaking a cross-sectional image of the composite (e.g., using scanningelectron microscopy, confocal microscopy, optical imaging, or otherimaging techniques) and dividing the cross-sectional area of the matrixmaterial by the cross-sectional area of the composite. Fibers in thefibrous region may be included in the cross-sectional area of the matrixmaterial. To facilitate identification of the matrix material, a coloredand/or fluorescent dye may be added to the matrix material.

The terms “comprise” (and any form of comprise, such as “comprises” and“comprising”), “have” (and any form of have, such as “has” and“having”), and “include” (and any form of include, such as “includes”and “including”) are open-ended linking verbs. As a result, an apparatusthat “comprises,” “has,” or “includes” one or more elements possessesthose one or more elements, but is not limited to possessing only thoseone or more elements. Likewise, a method that “comprises,” “h as,” or“includes” one or more steps possesses those one or more steps, but isnot limited to possessing only those one or more steps.

Any embodiment of any of the apparatuses, systems, and methods canconsist of or consist essentially of—rather thancomprise/have/include—any of the described steps, elements, and/orfeatures. Thus, in any of the claims, the term “consisting of” or“consisting essentially of” can be substituted for any of the open-endedlinking verbs recited above, in order to change the scope of a givenclaim from what it would otherwise be using the open-ended linking verb.With respect to the term “consisting essentially of,” a basic and novelcharacteristic of a fiber-reinforced composite of the present disclosureis its substantially uniform density, as defined by its mean RFAC (%)and COV (%).

Further, a device or system that is configured in a certain way isconfigured in at least that way, but it can also be configured in otherways than those specifically described.

The features of one embodiment may be applied to other embodiments, eventhough not described or illustrated, unless expressly prohibited by thisdisclosure or the nature of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate by way of example and not limitation.For the sake of brevity and clarity, every feature of a given structureis not always labeled in every figure in which that structure appears.Identical reference numbers do not necessarily indicate an identicalstructure. Rather, the same reference number may be used to indicate asimilar feature or a feature with similar functionality, as maynon-identical reference numbers. The figures are drawn to scale (unlessotherwise noted), meaning the sizes of the depicted elements areaccurate relative to each other for at least the embodiment(s) depictedin the figures.

FIG. 1 includes cross-sectional images of prior art unidirectionalfiber-reinforced composites.

FIG. 2 is a cross-sectional confocal microscope image of aunidirectional fiber-reinforced composite of the present disclosure.

FIG. 3 is a schematic of a unidirectional fiber-reinforced composite ofthe present disclosure, where a length, width, and thickness of thecomposite may be measured along axes E₁, E₂, and E₃, respectively.

FIG. 4A is a schematic of a stack or lay-up of three unidirectionalfiber-reinforced composites, with fibers of the three composites beingsubstantially parallel to each other.

FIG. 4B is a cut-away schematic of a stack or lay-up of twounidirectional fiber-reinforced composites, with fibers of the twocomposites being oriented in differing directions.

FIG. 4C is a schematic of a stack or lay-up of unidirectionalfiber-reinforced composites, including a protective coating.

FIG. 5 is a schematic of a system for making unidirectionalfiber-reinforced composites of the present disclosure.

FIG. 6A is a perspective view of a spreading unit of the presentdisclosure.

FIG. 6B is a cross-sectional side view of the spreading unit of FIG. 6A,taken along line 6B-6B of FIG. 6A.

FIGS. 6C-6G are side, top, bottom, front, and back views, respectively,of the spreading unit of FIG. 6A.

FIG. 7A is a perspective view of a spreading element of the presentdisclosure.

FIG. 7B is a cross-sectional end view of the spreading element of FIG.7A, taken along line 7B-7B of FIG. 7A.

FIGS. 7C-7F are front, top, bottom, and perspective views, respectively,of the spreading element of FIG. 7A.

FIG. 7G is a cross-sectional side view of the spreading element of FIG.7A, taken along line 7G-7G of FIG. 7A.

FIGS. 8A-8C are schematics of fiber bundle(s) being spread usingspreading elements of the present disclosure.

FIGS. 8D and 8E are perspective views of fiber bundles being spreadusing a spreading unit of the present disclosure.

FIG. 9 is a schematic depicting one embodiment for processing spreadedfiber layer(s) to form a unidirectional fiber-reinforced composite.

FIGS. 10A and 10B are perspective and front views, respectively, of arubbing element of the present disclosure.

FIG. 11 is a schematic depicting one embodiment for processing spreadedfiber layer(s) to form a unidirectional fiber-reinforced composite.

FIGS. 12-14 are cross-sectional confocal microscope images ofunidirectional fiber-reinforced composites of the present disclosure.

FIGS. 15-17 are cross-sectional confocal microscope images ofunidirectional fiber-reinforced composites that are comparative to thoseof the present disclosure.

FIGS. 18 and 19 are front and side views, respectively, of test samples,each including a laminate formed from unidirectional tapes of thepresent disclosure.

FIG. 20 depicts an apparatus suitable for testing the test samples ofFIGS. 18 and 19.

FIGS. 21 and 22 depict the test samples of FIGS. 18 and 19, aftertesting.

DETAILED DESCRIPTION

Currently available fiber-reinforced composites may suffer fromnon-uniform arrangements of fibers and voids that can render thecomposites weak and susceptible to cracks and breakage that canultimately lead to the failure of parts, components, devices, and thelike including such composites. By comparison, fiber-reinforcedcomposites of the present disclosure include a non-woven fibrous regionhaving a substantially uniform density as defined by a mean relativefiber area coverage (RFAC) (%) and a coefficient of variance (COV) (%).Composites of the present disclosure have improved structuralcharacteristics when compared with currently available composites.

Conventional apparatuses for spreading and/or impregnating fibers sufferfrom an inability to provide for sufficiently even spacing of the fibersand/or an inability to sufficiently prevent the fibers from movingduring impregnation. Such uneven spacing and fiber movement can resultin non-uniform fiber arrangement and voids in a resulting composite. Incontrast, the spreading unit and the impregnation unit of the presentdisclosure can be used to prepare fiber-reinforced composites havingsubstantially uniform densities, as described above.

These and other non-limiting aspects of the present invention arediscussed in further detail in the following sections.

A. Fiber-Reinforced Composites

Fiber-reinforced composites of the present disclosure can have athermoplastic or thermoset polymeric matrix and a non-woven fibrousregion comprising a plurality of continuous fibers dispersed in thepolymeric matrix. Typically, the width and the length of the non-wovenfibrous region are substantially similar to the width and the length,respectively, of the fiber-reinforced composite Such fiber-reinforcedcomposites can include, by volume, at least 35 to 70% of the pluralityof continuous fibers.

Such a non-woven fibrous region can have a substantially uniform densityas defined by a mean relative fiber area coverage (RFAC) (%) of from 65to 90 and a coefficient of variance (COV) (%) of from 3 to 20,preferably a mean RFAC (%) of from 69 to 90 and a COV (%) of from 3 to15, and most preferably a mean RFAC (%) of from 75 to 90 and a COV (%)of from 3 to 8.

1. Determining Density Uniformity

The density uniformities of the composites of the present disclosure aredetermined by using the following procedure:

-   -   1. A cross-sectional image of a thermoplastic or thermoset        fiber-reinforced tape/composite is obtained via optical        microscopy (e.g. confocal microscopy). The cross-sectional image        is taken perpendicularly to the longitudinal axis of the fibers        and has a length of at least 1500 μm and a width (e.g., measured        along a thickness of the tape/composite) of at least 160 μm. In        the Examples, a Keyence VK-X200 Camera with a 50× lens (Keyence        VK-X200, Elmwood, N.J., USA) was used; however, other cameras or        imaging devices can be used.    -   2. Cross hairs are drawn that bisect the length and the width of        the cross-sectional image.    -   3. A first square box is drawn centered on the cross hairs and        having sides equal to 40% of the thickness of the        tape/composite.    -   4. Two sets of 5 adjacent square boxes, each square box having        the same dimensions as the first square box, are drawn such that        each set is on a respective side of the vertical or width-wise        cross hair, adjacent to the first square box, and centered on        the horizontal or length-wise cross-hair. A total of 11 boxes        will be present, thereby offering 11 data points.    -   5. Fiber surface area, or the area occupied by fibers, in each        of the 11 square boxes is measured and, for each square box, is        represented as a percentage of the total area of the square box,        referred to as area coverage (AC) (%).    -   6. A relative fiber area coverage (RFAC) (%) for each of the 11        square boxes is determined by dividing AC for the square box by        the theoretical maximum possible AC, which may assume close        packing of circular filaments, and multiplying by 100. A mean        RFAC (%) is determined by averaging the RFACs of the 11 square        boxes.    -   7. A coefficient of variance (COV) (%) is determined by dividing        the standard deviation (σ) of the ACs by the average of the ACs        and multiplying by 100.

The above procedure was used in the Examples section to calculate themean RFAC and COV values of fiber-reinforced composites of the presentdisclosure and three comparative, commercially available composites.

2. Fiber-Reinforced Composite Dimensions

FIGS. 2 and 3 depict a unidirectional fiber-reinforced composite 200.Fiber-reinforced composites (e.g., 200) can have any width (e.g.,measured along axis E₂) and any length (e.g., measured along axis E₁).For example, fiber-reinforced composites (e.g., 200) can have a width ofup to 6 m or larger, or from 0.01 to 6 m, 0.5 to 5 m, or 1 to 4 m, orany range therebetween, and a length of up to 10,000 m or larger, orfrom 5 to 1,000 m, 10 to 100 m, or any range therebetween. The width ofa composite (e.g., 200) can be 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30,0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90,0.95, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 m, orlarger. The length of a composite (e.g., 200) can be 1, 10, 100, 500,1,000, 1,500, 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, 5,000, 5,500,6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000 meters,or larger.

3. Fibrous Region

Fiber-reinforced composite 200 includes a non-woven fibrous region 202dispersed in a polymer matrix 204. Non-woven fibrous region 202 includesa plurality of fibers 206, which are unidirectionally oriented andsubstantially parallel to a first axis (e.g., axis E₁, FIG. 3). Fibers(e.g., 206) of a composite (e.g., 200) make up, by volume, 35 to 70%,preferably 40 to 65%, more preferably 45 to 55%, or any rangetherebetween, of the composite. Fibrous region 202 can be formed from afirst flattened fiber layer and a second flattened fiber layer that havebeen pressed into a matrix material (e.g., as shown in and describedwith respect to FIG. 9). Fibers 206 can be glass fibers, carbon fibers,aramid fibers, polyethylene fibers, polyester fibers, polyamide fibers,ceramic fibers, basalt fibers, or steel fibers, or a combinationthereof. Fibers 206 can have an average filament cross-sectional area offrom 7 μm² to 800 μm², which, for circular fibers, equates to an averagefilament diameter of from 3 to 30 microns.

Fibers (e.g., 206) of a composite (e.g., 200) may be provided in bundles(e.g., bundles of carbon, ceramic, carbon precursor, ceramic precursor,glass, and/or the like fibers). Such bundles may include any number offibers, such as, for example, 400, 750, 800, 1,375, 1,000, 1,500, 3,000,6,000, 12,000, 24,000, 50,000, 60,000, or more fibers. Fibers in abundle can have an average filament diameter of 5, 6, 7, 8, 9, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or more microns(e.g., from 5 to 24 microns, 10 to 20 microns, 12 to 15 microns, or anyrange therebetween). Fibers can be provided with a coating (e.g. acoating of an organic polymer, such as an organosilane), a pigment,and/or the like.

Glass fiber bundles (e.g., fiber glass yarn bundles) are commerciallyavailable from PPG Industries (Pittsburgh, Pa., USA) under the tradename HYBON®, Jushi Group Co., Ltd. (CHINA), and Kripa International(INDIA). Glass fiber bundles can have an average filament diameter of10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 microns, orlarger (e.g., from 10 to 24 microns, 12 to 20 microns, 13 to 15 microns,or any range therebetween). Carbon fiber or modified carbon fiberbundles (e.g., carbon fiber tows) are commercially available from ACPComposites (Livermore, Calif., USA), Toray Industries, Inc. (JAPAN), andZOLTEK (Bridgeton, MO, USA) under the trade name Panex®. Carbon fiberbundles can have an average filament diameter of from 3 to 8 microns,from 6 to 7 microns, or any range therebetween.

Aramid fiber bundles (e.g., aramid fiber yarn bundles) are sold byDuPont™ (Wilmington, Del., USA) under the trade name KEVLAR®. Ceramicfiber bundles (e.g., metal oxide fiber bundles) are commerciallyavailable from 3M (United States) under the trade name 3M™ Nextel™Continuous Ceramic Oxide Fibers. Basalt fiber bundles are commerciallyavailable from Kamenny Vek (Moscow, RUSSIA) under the trade nameBasfiber® or from Sudaglass Fiber Technology under the trade nameSudaglass (RUSSIA). Polyester fiber bundles, polyamide fiber bundles,polypheylene sulfide fiber bundles, and polypropylene fiber bundles arecommercially available from Toray Industries under the trade nameTORAYCAm. Without wishing to be bound by theory, it is believed thatphysical properties of fibers do not substantially change when thefibers are processed to form a fiber-reinforced composite using methodsand apparatuses of the present disclosure.

A polymer matrix (e.g., 204) can comprise any suitable material, suchas, for example, a thermoplastic polymer and/or a thermoset polymer.Non-limiting examples of such thermoplastic polymers includepolyethylene terephthalate (PET), polycarbonates (PC), polybutyleneterephthalate (PBT), poly(1,4-cyclohexylidenecyclohexane-1,4-dicarboxylate) (PCCD), glycol modified polycyclohexylterephthalate (PCTG), poly(phenylene oxide) (PPO), polypropylene (PP),polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS),polymethyl methacrylate (PMMA), polyethyleneimine or polyetherimide(PEI) or derivatives thereof, thermoplastic elastomers (TPE),terephthalic acid (TPA) elastomers, poly(cyclohexanedimethyleneterephthalate) (PCT), polyethylene naphthalate (PEN), a polyamide (PA),polysulfone sulfonate (PSS), polyether ether ketone (PEEK), polyetherketone ketone (PEKK), acrylonitrile butyldiene styrene (ABS),polyphenylene sulfide (PPS), co-polymers thereof, or blends thereof.Non-limiting examples of such thermoset polymers include unsaturatedpolyester resins, polyurethanes, bakelite, duroplast, urea-formaldehyde,diallyl-phthalate, epoxy resin, epoxy vinylesters, polyimides, cyanateesters of polycyanurates, dicyclopentadiene, phenolics, benzoxazines,co-polymers thereof, or blends thereof.

Fibrous region 202 has a substantially uniform density as defined above.As shown, composite 200 has a volume fraction of voids that is less than5%, such as, for example, less than 4, 3, 2, or 1%, from 0 to 5%, from0.1 to 4%, or from 1 to 3%. Some fiber-reinforced composites, such ascomposite 200, can be substantially free of voids. In contrast, theprior art composites of FIG. 1 have fibrous regions that, whileincluding consistent density portions 102, have inconsistent densityportions 104 and voids 106.

4. Polymeric-Rich Regions

As shown, non-woven fibrous region 202 is positioned between a firstpolymeric-rich region 208 and a second polymeric-rich region 210.Polymeric-rich regions 208 and 210 include less than 10%, by volume, offibers 206. Polymeric-rich regions (e.g., 208, 210, and/or the like) cancomprise less than 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1%, by volume,of fibers (e.g., 206). The width and the length of each of first andsecond polymeric-rich regions, 208 and 210, are substantially similar tothe width and the length, respectively, of fiber reinforced composite200. For fiber-reinforced composite 200, a sum of the thickness of firstpolymeric-rich region 208 and the thickness of second polymeric-richregion 210 is from 15 to 25% of the thickness of the composite. Firstand second polymeric-rich regions, 208 and 210, have substantially thesame thickness (e.g., the thicknesses are within 10% of each other);however, in other embodiments, polymeric-rich regions (e.g., 208 and210) may have differing thicknesses (e.g., thicknesses that vary by morethan 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more % with respectto each other). Each of first and second polymeric-rich regions, 208 and210, can have a substantially uniform density throughout thepolymeric-rich region. Such polymer-rich regions (e.g., 208 and 210) mayenhance composite (e.g., 200) strength by providing sufficient polymericmatrix (e.g., 204) to hold fibers (e.g., 206) in position, as well asfacilitate handling of the composite (e.g., by overlying and containingfibers within the composite) and bonding of the composite to othercomposites or structures.

5. Fiber-Reinforced Composites Made from Plies

FIGS. 4A-4C are schematics of stacks or lay-ups of fiber-reinforcedcomposites of the present invention, which may be used to formlaminates. Such stacks or lay-ups can include two or more (e.g., 2, 3,4, 5, 6, 7, 8, 9, 10, or more) fiber-reinforced composites (e.g., 200),and such fiber-reinforced composites can be oriented relative to oneanother within the stack or lay-up in any suitable fashion. For example,stack 400 of FIG. 4A includes three UD fiber-reinforced composites, 200,402, and 404. As shown, fibers 406 of each UD composite 200, 402, and404 are substantially parallel to one another and with axis E₁ (e.g.,stack 400 may be characterized as a UD stack). For further example,stack 400 of FIG. 4B includes two UD fiber-reinforced composites, 200and 402. As shown, fibers 206 of UD composite 200 are angularly disposed(e.g., at 90 degrees) relative to fibers 406 of UD composite 402.Composites, plies, stacks, and laminates may be provided with protectivecoating(s). For example, FIG. 4C depicts a stack of two UDfiber-reinforced composites, 408 and 410, having protective coatings orlayers 412 and 414. Lay-ups or stacks having non-fibrous or non-UDlayer(s), plie(s), or film(s) are also contemplated. Examples of suchlayer(s), plie(s), or film(s) include neat thermoplastic resin,compounded thermoplastic polymer with various additives, and/or thelike.

6. Additives

The disclosed polymeric compositions and matrices can further compriseone or more optional additive components, including for example, one ormore additives selected from the group consisting of: a coupling agentto promote adhesion between a matrix material and fibers, anantioxidant, a heat stabilizer, a flow modifier, a flame retardant, a LVstabilizer, a UV absorber, an impact modifier, a cross-linking agent, acolorant, or a combination thereof. Non-limiting examples of couplingagents suitable for use as an additive component in the disclosedcompositions include Polybond® 3150 maleic anhydride graftedpolypropylene, commercially available from Chemtura, Fusabond® P613maleic anhydride grafted polypropylene, commercially available fromDuPont, maleic anhydride ethylene, or combinations thereof. An exemplaryflow modifier suitable for use as an additive component in the disclosedcompositions can include, without limitation, CR20P peroxidemasterbatch, commercially available from Polyvel Inc. A non-limitingexemplary stabilizer suitable for use as an additive component in thedisclosed compositions can include, without limitation, Irganox® B225,commercially available from BASF. In a still further aspect, neatpolypropylene can be introduced as an optional additive. Non-limitingexamples of flame retardants include halogen and non-halogen-basedpolymer modifications and additives. Non-limiting examples of UVstabilizers include hindered amine light stabilizers,hydroxybenzophenones, hydroxyphenyl benzotriazoles, cyanoacrylates,oxanilides, hydroxyphenyl triazines, and combinations thereof.Non-limiting examples of UV absorbers include4-substituted-2-hydroxybenzophenones and their derivatives, arylsalicylates, monoesters of diphenols, such as resorcinol monobenzoate,2-(2-hydroxyaryl)-benzotriazoles and their derivatives,2-(2-hydroxyaryl)-1,3,5-triazines and their derivatives, or combinationsthereof. Non-limiting examples of impact modifiers includeelastomers/softblocks dissolved in matrix-forming monomer(s), such as,for example, bulk HIPS, bulk ABS, reactor modified PP, Lomod, Lexan EXL,and/or the like, thermoplastic elastomers dispersed in matrix materialby compounding, such as, for example, di-, tri-, and multiblockcopolymers, (functionalized) olefin (co)polymers, and/or the like,pre-defined core-shell (substrate-graft) particles distributed in matrixmaterial by compounding, such as, for example, MBS, ABS-HRG, AA,ASA-XTW, SWIM, and/or the like, or combinations thereof. Non-limitingexamples of cross-linking agents include divinylbenzene, benzoylperoxide, alkylenediol di(meth)acrylates, such as, for example, glycolbisacrylate and/or the like, alkylenetriol tri(meth)acrylates, polyesterdi(meth)acrylates, bisacrylamides, triallyl cyanurate, triallylisocyanurate, allyl (meth)acrylate, diallyl maleate, diallyl fumarate,diallyl adipate, triallyl esters of citric acid, triallyl esters ofphosphoric acid, or combinations thereof.

B. Systems, Methods, and Apparatuses for Making Fiber-ReinforcedComposites

FIG. 5 is a schematic of a system 500 for making fiber-reinforcedcomposite 200 of the present disclosure. System 500 can include spoolsof fiber bundles 502, an unwinding unit 504, a fiber preparation section506, a spreading section 508, an impregnation section 510, a shapingunit 512, and a winder 514. Spools of fiber bundles 502 can bepositioned on unwinding unit 504, which can unwind fiber bundles 516from the spools such that the fiber bundles can be provided to fiberpreparation section 506. In some instances, a wound fiber bundle may beprovided (e.g., from a supplier) without a spool; in such instances, aspool may be inserted into the wound fiber bundle before positioning thewound fiber bundle on unwinding unit 504. Fiber bundles 516 may be fiberbundles that have not been subjected to any fiber spreading operation.Fiber preparation section 506 can include units known in the art toprepare fiber bundles 516 for spreading. For example, fiber preparationsection 506 may include one or more tensioners (e.g., a dancer tensioncontrol system, one or more rollers, and/or the like) for tensioning,stabilizing, and, in some instances, guiding fiber bundles 516. Suchtensioner(s) may provide tension to fiber bundles 516 during contactwith spreading elements 604A-604D, which may help maintain the fiberbundles in position during spreading or flattening of the fiber bundles.In some instances, unwinding unit 504 may be spaced from fiberpreparation section 506 and/or spreading section 508 (e.g., by 1, 2, 3,4, 5, 6, 7, 8, 9, 10, or more in), such that, for example, a weight offiber bundles 516 serves to tension the fiber bundles. For furtherexample, fiber preparation section 506 may be configured to heat fiberbundles 516 and/or spray the fiber bundles (e.g., to remove any coatingthat may be present on the fiber bundles).

In spreading section 508, fiber bundles 516 can be spread or flattenedinto spreaded fiber layers 518 (as described in more detail below).Spreaded fiber layers 518 may be provided to impregnation section 510,where the fiber layers can be dispersed into a matrix material to form afiber-reinforced composite 520 (e.g., fiber-reinforced composite 200 inFIG. 2). Impregnation section 510 can include an extruder, a bath, acoating system, and/or the like. Fiber-reinforced composite 520 canenter shaping unit 512, where the fiber-reinforced composite may beformed into a tape 522 or sheet. Tape 522 may be provided to winder 514,which may wind the tape around a spool (e.g., to facilitate storage,transportation, and/or the like of the tape).

1. Spreading Section

Spreading section 508 may include one or more spreading units 600, eachconfigured to spread one or more fiber bundles 516 into one or morespreaded fiber layers 518. Spreading section 508 may also include one ormore rollers, motors, electrical connections, and/or the like needed tooperate spreading unit 600.

i. Spreading Unit

Referring to FIGS. 6A through 6G, spreading unit 600 is depicted. Aswill be described in more detail below, spreading unit 600 can includevarious components, such as, for example, one or more holding elements(e.g., 602A-602D), one or more spreading elements (e.g., 604A-604D), oneor more heat sources (e.g., such as heated spreading element(s)), and,optionally, one or more rollers (e.g., 606). Components of spreadingunit 600 can be made of materials that are resistant to corrosion and/orto materials used in making fiber layers or fiber-reinforced composites(e.g, fibers, matrix materials, and/or the like), such as, for example,stainless steel, other alloys, and/or the like. Components of spreadingunit 600 can be coupled to a frame 608. One or more components ofspreading unit 600 can be removably coupled to frame 608, to, forexample, facilitate maintenance and/or reconfiguration of the spreadingunit (e.g., via replacing spreading elements with other spreadingelements having differing lobes, replacing holding elements with otherholding elements having differing fiber holding sections, radii, and/orthe like, and/or the like). Frame 608 can include wheels or otherfeatures to enhance portability of spreading unit 600.

ii. Holding Elements

Holding elements 602A-602D each include a fiber holding section 610disposed between holding element end sections 612 (FIG. 6F). For eachholding element, fiber holding section 610 may be characterized asincluding a plurality of grooves 614 or a plurality of projections 616.As shown, each fiber holding section 610 includes seven (7) grooves 614;however, in other embodiments, a fiber holding section (e g, 610) mayinclude any number of grooves (e.g., 614), and the number of grooves maybe selected based on a number of fiber bundles (e.g., 516) to be spreadby a spreading unit (e.g., 600), a number of spreaded fiber layers(e.g., 518) to be produced by the spreading unit, and/or the like.Grooves 614 of a fiber holding section 610 may each have dimensions(e.g., width and depth) that are the same as, substantially similar to,or different than one another. Holding elements 602A-602D each comprisea bar (e.g., the holding elements are rod-shaped); however, in otherembodiments, a holding element (e.g., 602A-602D) may comprise a plate.

Holding elements 602A-602D may each be configured to reduce undesiredlateral movement of a plurality of fibers (e.g., in a fiber bundle 516or a spreaded fiber layer 518) as the plurality of fibers enters thespreading unit, passes over spreading element(s), exits the spreadingunit, and/or the like. For example, for a fiber holding section 610,grooves 614 may each have a width (e.g., measured along a longitudinalaxis of the respective holding element) that corresponds to a width of aplurality of fibers that the fiber holding section is configured toreceive. Grooves 614 of holding elements 602A and 602C, which areconfigured to receive fiber bundles 516, may each have a smaller widththan a width of grooves 614 of holding elements 602B and 602D, which areconfigured to receive spreaded fibers from spreading elements 604A and604C. More particularly, grooves 614 of holding elements 602A and 602Ccan each have a width of 4 to 8 mm, preferably about 6 mm, and grooves614 of holding elements 602B and 602D can each have a width of 8 to 12mm, preferably about 10 mm.

Spreading unit 600 includes four (4) holding elements 602A-602D and four(4) spreading elements 604A-604D. Each spreading element can be pairedwith a holding element and, for each pair, the holding element can bepositioned upstream of the spreading element.

iii. Spreading Elements

Referring additionally to FIGS. 7A-7F, shown is a spreading element 604,which may be representative of spreading elements 604A-604D. Spreadingelement 604 is configured to spread a plurality of fibers into aspreaded fiber layer 518 (e.g., whether spreading fibers in a fiberbundle 516 or further spreading fibers in a spreaded fiber layer 518).Spreading element 604 includes a profile taken perpendicularly to alongitudinal axis of the spreading element, a first surface 626 thatdefines a convex portion of the profile, and a second surface 628 thatdefines a straight or concave portion of the profile. First surface 626can be ellipsoidal and/or second surface 628 can be planar or concave.First surface 626 and second surface 628 can meet at an edge 630, whichmay be rounded (e.g., the edge may be filleted) to mitigate snagging ortearing of fibers as they pass over the edge. In these ways and others,as a plurality of fibers passes over spreading element 604 (e.g.,approaching the spreading element in a direction indicated by arrow632), the fibers may transition from first surface 626 to second surface628 (e.g., across edge 630, if present), thereby spreading the fibers.Spreading element 604 is generally straight, for example, thelongitudinal axis of the spreading element extends through spreadingelement end sections 622 as well as a portion of the spreading elementthat is halfway between the longitudinal end sections. Spreading element604 comprises a bar (e.g., is rod-shaped); however, in otherembodiments, a spreading element (e.g., 604A-604D) may comprise a plate.

Spreading element 604 includes two or more lobes 620 disposed along thelongitudinal axis of the spreading element. Each lobe 620 can include afirst surface 626 and a second surface 628 (e.g., as described above).Lobes 620 can be disposed along the longitudinal axis of the spreadingelement such that second surfaces 628 of the two or more lobes arecontiguous. As shown, spreading element 604 includes 7 lobes; however,in other embodiments, a spreading element (e.g., 604) can include anysuitable number of lobes (e.g., 620), such as, for example, from 1 to100, 2 to 50, 3 to 25, 5 to 20 lobes, with 5, 6, 7, 8, 9, or 10 lobesbeing preferred.

Spreading elements 604A-604D can each be movable relative to a pluralityof fibers being spread by spreading unit 600 in a direction that issubstantially perpendicular to a long dimension of the fibers (e.g.,generally in a direction indicated by arrow 605), which may enhancespreading of the fibers. For example, each of spreading elements604A-604D may be coupled to frame 608 such that the spreading element ismovable relative to the frame in a direction that is substantiallyaligned with the longitudinal axis of the spreading element. In someembodiments, an entire spreading unit (e.g., 600), including a frame(e.g., 608) and spreading elements (e.g., 604A-604D), may be configuredto move relative to a plurality of fibers being spread by the spreadingunit.

More particularly, spreading elements 604A-604D may be configured tooscillate relative to a plurality of fibers being spread by spreadingunit 600. Such oscillation can be at any suitable amplitude, such as,for example, of from 0.1 to 20 mm, 0.1 to 10 mm, 0.5 to 8 mm, 1 to 5 mm,or 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4,1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8,2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2,4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6,5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0,7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4,8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8,9.9, 10.0, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm. Suchoscillation can be at any suitable frequency, such as, for example, offrom 0.1 to 5 Hz, 0.5 to 2 Hz, or 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5,3.0, 3.5, 4.0, 4.5, or 5.0 Hz. Such oscillation of spreading elements604A-604D may assist in juxtaposing a plurality of fibers as the fiberspass over the spreading elements. Each of spreading elements 604A-604Dcan be oscillated at a same or different amplitude and/or frequency.

Spreading elements 604A-604D can each be rotatable about thelongitudinal axis of the spreading element and relative to a pluralityof fibers being spread by spreading unit 600. For example, spreadingelements 604A-604D are each coupled to frame 608 such that the spreadingelement is rotatable relative to the frame about the longitudinal axisof the spreading element. Through such rotation of a spreading element,the location where a plurality of fibers makes contact with thespreading element (e.g., along first surface 626 or second surface 628or at edge 630) can be adjusted to provide for optimum spreading of thefibers. In some embodiments, such rotation of a spreading element may becyclical or oscillating.

Movement (e.g., translation and/or rotation) of spreading elements(e.g., 604A-604D) can be accomplished in any suitable fashion. Forexample, spreading element ends 622 of each spreading element 604A-604Dinclude coupling elements, 618A-618D, respectively, each configured tobe coupled to a motor or drive (not shown).

Referring additionally to FIG. 8A, methods for producing a spreadedfiber layer are shown. A fiber bundle 802 having an initial width(W_(i)) may enter spreading unit 600 and, in some instances, pass over aholding element (e.g., 602A-602D). Fiber bundle 802 may make contactwith spreading element 604A (e.g., travelling in a direction indicatedby arrow 607), which may be oscillating, at first surface 626 andtransition to second surface 628 (e.g., across edge 630), thereby beingspread into a spreaded fiber layer 804. Spreaded fiber layer 804 can, insome instances after passing over a holding element (e.g., 602A-602D),make contact with spreading element 604B, which may be oscillating, atfirst surface 626 and transition to second surface 628 (e.g., acrossedge 630), thereby being spread into a spreaded fiber layer 806, havinga width (W₁) that is larger than the initial width of fiber bundle 802.

While not shown, a (e.g., major and/or minor) radius of first surface626 of spreading element 604B (e.g., of lobe 620C) can be larger than acorresponding radius of first surface 626 of spreading element 604A(e.g., of lobe 620A). Such a configuration may facilitate spreadingelement 604B in further spreading spreaded fiber layer 804 fromspreading element 604A. A radius of first surface 626 of spreadingelement 604B can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more % larger thana corresponding radius of first surface 626 of spreading element 604A.In some embodiments, a first surface (e.g., 626) of a first spreadingelement (e.g., 604A) can have a radius of from 10 to 50 mm, 20 to 40 mm,25 to 35 mm, or about 30 mm and a first surface (e.g., 626) of a secondspreading element (e.g., 604B) that is downstream of the first spreadingelement can have a radius of from 50 to 100 mm, 50 to 90 mm, 55 to 65mm, or about 60 mm

In some embodiments, more than one fiber bundle (e.g, 516) can be usedto make a single spreaded fiber layer (e.g., 518). For example, andreferring additionally to FIGS. 8B-8E, fiber bundles 802 and 808 may bespread by spreading unit 600 into spreaded fiber layers 806 and 810,respectively (e.g., in a same or similar fashion as described above forfiber bundle 802). As shown, spreading elements 604A and 604B, and moreparticularly lobes 620A-620D thereof, may be positioned relative to oneanother such that spreaded fiber layers 806 and 810 form a singlespreaded fiber layer 812. Spreaded fiber layer 812 can have a width thatis equal to or greater than a sum of the width of spreaded fiber layer806 and a width (W₂) of spreaded fiber layer 810. Similarly, a spreadedfiber layer 812 can be formed from fiber bundles 816 and 818 (FIG. 8C).In some instances, spreaded fiber layer 812 from fiber bundles 802 and808 may be combined with spreaded fiber layer 812 from fiber bundles 816and 818 to form a spreaded fiber layer 812 having fibers from fiberbundles 802, 808, 816, and 818.

Such spreaded fiber layers (e.g., 806, 810, 812, and/or the like) may beproduced at any suitable rate, such as, for example, of from 1 to 50m/min, 2 to 25 m/min, or 8 to 15 m/min. Spreaded fiber layers (e.g.,806, 810, 812, and/or the like) from spreading section 508 may beprovided to impregnation section 510 to be dispersed into a matrixmaterial.

2. Impregnation Section

Impregnation section 510 may include an extruder 906, one or morepressing elements (e.g., 908, 914, 918, 922, 923, and/or the like), oneor more rubbing elements (e.g., 916, 920, 924, and/or the like), one ormore heat source(s) (e.g., 915, heated pressing element(s), heatedrubbing element(s), and/or the like), and/or the like. Impregnationsection 510 may also include one or more rollers, motors, electricalconnections, and/or the like needed to operate the impregnation section.At least some components of impregnation section 510 may be referred tocollectively as an impregnation unit, even though such components maynot be physically attached to one another.

Referring to FIG. 9, spreaded fiber layer(s) from spreading section 508may be guided to impregnation section 510 by one or more rollers 606(e.g., which, if present, may be considered a component of the spreadingsection and/or a component of the impregnation section) wherein thespreaded fiber layer(s) may be dispersed within a matrix material. Forexample, impregnation section 510 comprises an extruder 906 configuredto supply a sheet or film of matrix material to the spreaded fiberlayer(s); however, in other embodiments, a matrix material may beprovided to spreaded fiber layer(s) using any suitable structure.

Impregnation section 510 includes one or more pressing elements (e.g.,908, 914, 918, 922, 923, and/or the like), each disposed downstream ofextruder 906 and configured to press at least one of the spreaded fiberlayer(s) into the matrix material. For example, each pressing elementcan include a convex surface configured to press at least one of thespreaded fiber layer(s) into the matrix material as the spreaded fiberlayer, when in contact with the matrix material, is passed under tensionover the convex surface. A pressure applied by a pressing element to thespreaded fiber layer(s) can be varied by adjusting an angle at which thespreaded fiber layer(s) approach or leave the pressing element, atension of the spreaded fiber layer(s), and/or the like. Pressingelements (e.g., 908, 914, 918, 922, 923, and/or the like) may be heated,in some instances, to differing temperatures. In these ways and others,such pressing elements may provide sufficient pressure and/ortemperature to press the one or more spreaded fiber layers into thematrix material. In some instances, a heat source 915, such as, forexample, an infrared heat source, may be provided to facilitate thepressing process (e.g., by heating the matrix material and/or spreadedfiber layer(s)). Pressing elements (e.g., 908, 914, 918, 922, 923,and/or the like) may comprise any suitable structure, such as, forexample, a bar, plate, roller (e.g., whether stationary or rotating),and/or the like. In instances where a rotating pressing element isused—or any other rotating element that contacts fibers—a guard,barrier, or blade may be positioned against the rotating element toprevent fibers from wrapping around the rotating element.

Impregnation section 510 includes one or more rubbing elements (e.g.,916, 920, 924, and/or the like) configured to facilitate dispersion ofthe one or more spreaded fiber layers within the matrix material. FIGS.10A and 10B depict a rubbing element 1200, which may be representativeof rubbing elements 916, 920, and 924. Rubbing element 1200 includes twoor more convexities 1206 disposed along a longitudinal axis 1204 of therubbing element. Due to convexities 1206, rubbing element 1200 can havea profile, taken parallel to longitudinal axis 1204, that includescurved portions, which can collectively form a larger portion of theprofile that may be characterized as fluctuating and/or undulating(e.g., in distance from the longitudinal axis). Convexities 1206 ofrubbing element 1200 each include an ellipsoidal surface; however,convexities (e.g., 1206) of a rubbing element (e.g., 1200) may have anysuitable shape. Rubbing element 1200 comprises a bar (e.g., the rubbingelement is rod-shaped); however, in other embodiments, a rubbing elementmay comprise a plate.

One or more rubbing elements (e.g., 916, 920, 924, and/or the like) mayeach be movable relative to spreaded fiber layer(s) being processed byimpregnation section 510 in a direction that is substantiallyperpendicular to a long dimension of the spreaded fiber layer(s). Forexample, impregnation section 510 can include a frame to which the oneor more rubbing elements may be coupled, and each of the rubbingelement(s) can be movable relative to the frame in a direction that issubstantially aligned with the longitudinal axis of the rubbing element.Rubbing elements may be configured to oscillate, for example, at any ofthe amplitudes and frequencies described above for spreading elements604A-604D. Each rubbing element (e.g., 916, 920, 924, and/or the like)is configured to contact at least one of the one or more spreaded fiberlayers after the spreaded fiber layer has been pressed into the matrixmaterial.

As shown in FIG. 9, spreaded fiber layers 901 and 902 can be guided byrollers 606, if present, to extruder 906. Spreaded fiber layers 901 and902 can include the same or differing types of fibers and can have thesame or differing widths. Extruder 906 may supply a sheet or film ofmatrix material to at least one of spreaded fiber layers 901 and 902,such as, for example, to an upper surface of spreaded fiber layer 902 toform a coated spreaded fiber layer 910. Spreaded fiber layer 901 may bebrought into contact with coated spreaded fiber layer 910 and may bepressed into the matrix material by passing over pressing element 908.Coated spreaded fiber layer 910 may be pressed into the matrix materialby passing over pressing element 914. The spreaded fiber layers, coupledby the matrix material, may be passed over rubbing element 916, whichmay be oscillating, to facilitate dispersion of the spreaded fiberlayers into the matrix material. In this example, the coupled spreadedfiber layers may be further passed over pressing element 918, overrubbing element 920, over pressing element 922, over rubbing element924, and over pressing element 923. In some instances, the coupledspreaded fiber layers can be passed over a plate 925 and/or be directedto a pressing device 926 including one or more consolidation rollers928. A fiber-reinforced composite 200 from impregnation section 510 canbe processed by shaping unit 512 and/or provided to winder 514. In someembodiments, only one spreaded fiber layer (e.g., 901 or 902) isprocessed by impregnation section 510.

Referring now to FIG. 11, in some embodiments, an impregnation section510 includes a matrix material bath 1002. As shown, spreaded fiber layer902 can be passed through matrix material bath 1002, which can befacilitated by stationary or rotating rollers (e.g., 1004, 1006, and/orthe like), to form coated spreaded fiber layer 1008. Coated spreadedfiber layer 1008 may be consolidated, for example, by pressing (e.g.,via consolidation rollers 1010) to form fiber-reinforced composite 200.Fiber-reinforced composite 200 may be passed through a solvent recoverybath 1004 to remove any free matrix material, which can be facilitatedby stationary or rotating rollers (e.g., 1012 and/or the like).

EXAMPLES

The present invention will be described in greater detail by way ofspecific examples. The following examples are offered for illustrativepurposes only and are not intended to limit the invention in any manner.Those of skill in the art will readily recognize a variety ofnoncritical parameters which can be changed or modified to yieldessentially the same results.

Example 1 Sample Tapes of the Present Disclosure and Comparative Tapes

Unidirectional glass fiber tapes of the present disclosure (samples 1-3or S1-S3) were prepared using the spreading and impregnation unitsdescribed above. For S1-S3, the glass fibers have an average diameter of17 μm. For S, the polymer used to form the matrix was polypropylene, forS2, the polymer used to form the matrix material was high-densitypolyethylene, and, for S3, the polymer used to form the matrix materialwas polyamide 6 (Aegis® H8202NLB). FIGS. 12-14 are cross-sectionalconfocal microscope images of S1, S2, and S3, respectively, the imagesbeing obtained by a Keyence VK-X200 camera with a 50× lens.

Three comparative commercially available glass fiber tapes (comparatives1-3 or C1-C3) were also analyzed. Sample C1 has an average filamentdiameter of 13 μm, and samples C2 and C3 have an average filamentdiameter of 17 μm. FIGS. 15-17 are cross-sectional confocal microscopeimages of C1, C2 and C3, respectively.

The uniform densities of S1-S3 and C1-C3 were determined in the manneroutlined above in the section of the specification titled “DeterminingDensity Uniformity.” For S1, the RFAC (%) and COV (%) values are 82.3and 4.0, respectively. For S2, the RFAC (%) and COV (%) values are 80.4and 7.0, respectively. For S3, the RFAC (%) and COV (%) values are 69.7and 8.0, respectively. For C1, the RFAC (%) and COV (%) values are 47.3and 25.3, respectively. For C2, the RFAC (%) and COV (%) values are 65.7and 32.4, respectively. For C3, the RFAC (%) and COV (%) values are 55.5and 9.2, respectively.

Tables 1-3 provide the data points for S1-S3, respectively, and tables4-6 provide the data points for C1-C3, respectively. The theoreticalmaximum possible coverage, assuming close packing of circular filamentswithin a square, is 78.5%, which is calculated as the area of thecircular filaments divided by the area of square. For example, for acircular filament with a radius ‘r’ within a square having a side ‘2r,’the coverage equals πr²/(2r)².

TABLE 1 (Sample S1 Data Points) Fiber Area Square Area Fiber Percent BoxFiber Count (cm²) (cm²) Coverage* 1 30  6.8094E−05 0.0001 68.1 2 30 6.8094E−05 0.0001 68.1 3 29 6.58242E−05 0.0001 65.8 4 29 6.58242E−050.0001 65.8 5 27 6.12846E−05 0.0001 61.3 6 27 6.12846E−05 0.0001 61.3 728 6.35544E−05 0.0001 63.6 8 28 6.35544E−05 0.0001 63.6 9 27 6.12846E−050.0001 61.3 10 29 6.58242E−05 0.0001 65.8 11 29 6.58242E−05 0.0001 65.8*Average of boxes 1 to 11 is 64.6. Therefore, (64.6/78.5) × 100 = anRFAC of 82.3. Standard deviation for boxes 1 to 11 is 2.6. Therefore,(2.6/64.4) × 100 = a COV of 4.0.

TABLE 2 (Sample S2 Data Points) Fiber Area Square Area Fiber Percent BoxFiber Count (cm²) (cm²) Coverage* 1 27 6.12846E−05 0.0001 61.3 2 286.35544E−05 0.0001 63.6 3 29 6.58242E−05 0.0001 65.8 4 28 6.35544E−050.0001 63.6 5 27 6.12846E−05 0.0001 61.3 6 30 6.80940E−05 0.0001 68.1 726 5.90148E−05 0.0001 59.0 8 29 6.58242E−05 0.0001 65.8 9 27 6.12846E−050.0001 61.3 10 31 7.03638E−05 0.0001 70.4 11 24 5.44752E−05 0.0001 54.5*Average of boxes 1 to 11 is 63.1. Therefore, (63.1/78.5) × 100 = anRFAC of 80.4. Standard deviation for boxes 1 to 11 is 4.4. Therefore,(4.4/63.1) × 100 = a COV of 7.0.

TABLE 3 (Sample S3 Data Points) Fiber Area Square Area Fiber Percent BoxFiber Count (cm²) (cm²) Coverage* 1 25  5.6745E−05 0.0001 56.7 2 265.90148E−05 0.0001 59.0 3 27 6.12846E−05 0.0001 61.3 4 24 5.44752E−050.0001 54.5 5 22 4.99356E−05 0.0001 49.9 6 25 5.67450E−05 0.0001 56.7 726 5.90148E−05 0.0001 59.0 8 24 5.44752E−05 0.0001 54.5 9 23 5.22054E−050.0001 52.2 10 22 4.99356E−05 0.0001 49.9 11 21 4.76658E−05 0.0001 47.7*Average of boxes 1 to 11 is 54.7. Therefore, (54.7/78.5) × 100 = anRFAC of 69.7. Standard deviation for boxes 1 to 11 is 4.4. Therefore,(4.4/54.7) × 100 = a COV of 8.0.

TABLE 4 (Comparative Sample C1 Data Points) Fiber Area Square Area FiberPercent Box Fiber Count (cm²) (cm²) Coverage* 1 32 4.25E−05 0.0001 42.52 17 2.26E−05 0.0001 22.6 3 24 3.19E−05 0.0001 31.9 4 31 4.11E−05 0.000141.1 5 37 4.91E−05 0.0001 49.1 6 31 4.11E−05 0.0001 41.1 7 21 2.79E−050.0001 27.9 8 17 2.26E−05 0.0001 22.6 9 33 4.38E−05 0.0001 43.8 10 354.65E−05 0.0001 46.5 11 30 3.98E−05 0.0001 39.8 *Average of boxes 1 to11 is 37.2. Therefore, (37.2/78.5) × 100 = an RFAC of 47.3. Standarddeviation for boxes 1 to 11 is 9.4. Therefore, (9.4/37.2) × 100 = a COVof 25.3.

TABLE 5 (Comparative Sample C2 Data Points) Fiber Area Square Area FiberPercent Box Fiber Count (cm²) (cm²) Coverage* 1 28 6.36E−05 0.0001 63.62 16 3.63E−05 0.0001 36.3 3 30 6.81E−05 0.0001 68.1 4 11  2.5E−05 0.000125.0 5 21 4.77E−05 0.0001 47.7 6 28 6.36E−05 0.0001 63.6 7 29 6.58E−050.0001 65.8 8 25 5.67E−05 0.0001 56.7 9 29 6.58E−05 0.0001 65.8 10 235.22E−05 0.0001 52.2 11 10 2.27E−05 0.0001 22.7 *Average of boxes 1 to11 is 51.6. Therefore, (51.6/78.5) × 100 = an RFAC of 65.7. Standarddeviation for boxes 1 to 11 is 16.7. Therefore, (16.7/51.6) × 100 = aCOV of 32.4.

TABLE 6 (Comparative Sample C3 Data Points) Fiber Area Square Area FiberPercent Box Fiber Count (cm²) (cm²) Coverage* 1 21 4.77E−05 0.0001 47.72 21 4.77E−05 0.0001 47.7 3 19 4.31E−05 0.0001 43.1 4 18 4.09E−05 0.000140.9 5 17 3.86E−05 0.0001 38.6 6 18 4.09E−05 0.0001 40.9 7 17 3.86E−050.0001 38.6 8 22 4.99E−05 0.0001 49.9 9 19 4.31E−05 0.0001 43.1 10 214.77E−05 0.0001 47.7 11 18 4.09E−05 0.0001 40.9 *Average of boxes 1 to11 is 43.5. Therefore, (43.5/78.5) × 100 = an RFAC of 55.5. Standarddeviation for boxes 1 to 11 is 4.0. Therefore, (4.0/43.5) × 100 = a COVof 9.2.

Example 2 Process to Make S1

Samples S1-S3 were prepared using the spreading and impregnation unitsdescribed above. The following includes anon-limiting explanation of theprocedure used to make sample S1.

A desired number of fiber bundles are introduced into the UD tapeproduction line. Fibers from the fiber bundles are continuously pulledthrough the production line by a pulling station located at the end ofthe production line. The fibers are separated into two groups, one ofwhich is processed by the lower section of the spreading unit to producea lower spreaded fiber layer and the other of which is processed by theupper section of the spreading unit to produce an upper spreaded fiberlayer. A polymer matrix material is brought into contact with the topsurface of the lower spreaded fiber layer. The upper and lower spreadedfiber layers are combined and pressed into the matrix material bypassing over a series of pins. The combined spreaded fiber layers areconsolidated into a UD tape, which is wound around a spool. Line speedused to make sample S1 was 8 m/s.

Example 3 Testing of Laminates Comprising Tapes of the PresentDisclosure

Referring now to FIGS. 18-22, compression testing of laminatescomprising tapes of the present disclosure was performed. Four testsamples 1104 were prepared, each including a UD laminate 1120 havingfibers aligned with a long dimension of the laminate. Each laminate 1120was formed from a 4 mm thick lay-up of UD tapes of the presentdisclosure, each having glass fibers dispersed within a polypropylenematrix material. Each laminate 1120 was cut to a length of 140 mm and awidth of 12 mm using a water jet cutter. To prepare each laminate 1120for testing, aluminum tabs 1116 were adhered to the laminate at opposinglaminate ends 1112 using 3M Scotch-Weld DP8005. Prior to adhesion ofaluminum tabs 1116, each laminate end 1112 was scuffed and degreased.For each test sample 1104, a gage section 1108 was defined betweenopposing sets of aluminum tabs 1116.

Samples 1104 were compression tested until failure using a Zwick 250 kNtesting apparatus 1124 (FIG. 20). The mean compression strength ofsamples 1104 was 456 MPa, with a standard deviation of 45.4 MPa. Asshown in FIGS. 21 and 22, for each sample 1104, failure occurred at oneof laminate ends 1112 rather than at gage section 1108, which may beattributed to de-bonding between the laminate end and respectivealuminum tab(s) 1116. It is anticipated that, through use of more robusttabs (e.g., forming the tabs with the laminate, molding the tabs ontothe laminate, welding the tabs to the laminate, and/or the like), highercompression strength test results could be achieved.

The above specification and examples provide a complete description ofthe structure and use of illustrative embodiments. Although certainembodiments have been described above with a certain degree ofparticularly, or with reference to one or more individual embodiments,those skilled in the art could make numerous alterations to thedisclosed embodiments without departing from the scope of thisinvention. As such, the various illustrative embodiments of the methodsand systems are not intended to be limited to the particular formsdisclosed. Rather they include all modifications and alternativesfalling within the scope of the claims, and embodiments other than theone shown may include some or all of the features of the depictedembodiment. For example, elements may be omitted or combined as aunitary structure and/or connections may be substituted. Further, whereappropriate, aspects of any of the examples described above may becombined with aspects of any of the other examples described to formfurther examples having comparable or different properties and/orfunctions, and addressing the same or different problems. Similarly, itwill be understood that the benefits and advantages described above mayrelate to one embodiment or may relate to several embodiments.

The claims are not intended to include, and should not be interpreted toinclude, means-plus- or step-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase(s)“means for” or “step for,” respectively.

The invention claimed is:
 1. An impregnation unit configured to receiveat least first and second spreaded fiber layers and to disperse thefirst and second spreaded fiber layers into a matrix material, theimpregnation unit comprising: an extruder configured to supply a sheetor film of the matrix material between the first and second spreadedfiber layers; a first pressing element disposed downstream of theextruder, the first pressing element having a convex surface configuredto press the first spreaded fiber layer into the matrix material; asecond pressing element disposed downstream of the extruder, the secondpressing element having a convex surface configured to press the secondspreaded fiber layer into the matrix material; a frame; and one or morerubbing elements coupled to the frame, each having one or moreconvexities disposed along a longitudinal axis of the rubbing elementwherein each of the one or more rubbing elements is movable relative tothe frame in a direction that is substantially aligned with thelongitudinal axis of the rubbing element and wherein each of the one ormore rubbing elements is configured to contact at least one of the firstand second spreaded fiber layers after the spreaded fiber layer has beenpressed into the matrix material.
 2. The impregnation unit of claim 1,wherein the second pressing element is disposed downstream of the firstpressing element.
 3. The impregnation unit of claim 1, wherein each ofthe first and second pressing elements comprise a bar or a plate.
 4. Theimpregnation unit of claim 1, wherein at least one of the first andsecond pressing elements is configured to be heated.
 5. The impregnationunit of claim 1, comprising a heat source configured to melt the sheetor film of the matrix material.
 6. An impregnation unit configured toreceive one or more spreaded fiber layers and to disperse the one ormore spreaded fiber layers into a matrix material, the impregnation unitcomprising: an extruder configured to supply a sheet or film of thematrix material; one or more pressing elements disposed downstream ofthe extruder, each having a convex surface configured to press at leastone of the one or more spreaded fiber layers into the matrix material; aframe; and one or more rubbing elements coupled to the frame, eachhaving one or more convexities disposed along a longitudinal axis of therubbing element; wherein each of the one or more rubbing elements ismovable relative to the frame in a direction that is substantiallyaligned with the longitudinal axis of the rubbing element; and whereineach of the one or more rubbing elements is configured to contact atleast one of the one or more spreaded fiber layers after the spreadedfiber layer has been pressed into the matrix material.
 7. Theimpregnation unit of claim 6, wherein: the extruder is configured tosupply the sheet or film of a matrix material between first and secondones of the one or more spreaded fiber layers; and the one or morepressing elements comprises: a first pressing element configured topress the first spreaded fiber layer into the matrix material; and asecond pressing element configured to press the second spreaded fiberlayer into the matrix material.
 8. The impregnation unit of claim 7,wherein the second pressing element is disposed downstream of the firstpressing element.
 9. The impregnation unit of claim 6, wherein, for eachof the one or more rubbing elements, each of the one or more convexitiescomprises an ellipsoidal surface.
 10. The impregnation unit of claim 6,wherein each of the one or more rubbing elements comprises a bar or aplate.
 11. The impregnation unit of claim 6, wherein at least one of theone or more rubbing elements is configured to be heated.